1. Field of the Invention
This invention relates to a silica dispersion, a method for preparing the same and a method for making an ink-jet recording material using the same.
2. Prior Art
A dispersion of silica fine particles can be generally prepared by primarily dispersing (premixing) silica fine particles in a dispersing medium (water, an organic solvent or a mixture thereof) to form a slurry of silica fine particles, and then, secondary dispersing the slurry of the silica fine particles by a dispersing machine such as a high-pressure homogenizer, a ball mill, etc.
A silica dispersion can be used as an abrasive for grinding a semiconductor wafer represented by silicon or an insulating layer in the course of producing IC; a hard coating agent for plastics such as eyeglass lenses, etc.; a coating agent for an ink jet recording material or an OHP (overhead projector); and further for an anti-blocking agent for various kinds of films; an adhesive aid for glass fibers, etc.; and a stabilizer for an emulsion, a wax, etc.
On the other hand, an ink-jet recording system has been abruptly spread over various fields. It has been also known to use silica fine particles for an ink-receptive layer of an ink-jet recording material. For example, there have been proposed recording materials obtained by coating silica fine particles and a hydrophilic binder onto a paper support as disclosed in Japanese Provisional Patent Publications No. 51583/1980, No. 157/1981, No. 107879/1982, No. 107880/1982, No. 230787/1984, No. 160277/1987, No. 184879/1987, No. 183382/1987, No. 11877/1989, and the like.
Also, in Japanese Patent Publication No. 56552/1991, Japanese Provisional Patent Publications No. 188287/1990, No. 20306/1998, No. 81064/1998, No. 100397/1998, No. 119423/1998 and No. 203006/1998, there have been disclosed ink-jet recording sheets using synthetic silica fine particles prepared by a gas phase process (hereinafter referred to as xe2x80x9cfumed silicaxe2x80x9d). The fumed silica is ultrafine particles having an average particle diameter of a primary particle of several nm to several tens nm, and has characteristics of easily giving high gloss.
An ink-jet recording material has generally been prepared by coating a coating solution for forming an ink-receptive layer on a support and drying. The coating solution for forming an ink-receptive layer has been known to be prepared by adding a hydrophilic binder (e.g., an aqueous polyvinyl alcohol solution, etc.) or other additives (e.g., a cationic polymer, a hardening agent, a surfactant, etc.) to the above-mentioned dispersion of silica fine particles and dispersing the mixture (see the above-mentioned references).
In the field of the ink-jet recording materials, a photo-like material has been desired in recent years. That is, a recording material having high gloss, high chroma and high ink absorption property has been desired. It is suitable to use an ultrafine silica particle having an average primary particle diameter of 50 nm or less for obtaining characteristics satisfying the above demands, and, for example, fumed silica has preferably been used. However, a dispersion of ultrafine silica particles involves the problems that stability of the dispersion is poor and silica fine particles are liable to be aggregated. As the result, many problems arise that coating failure including cissing, stripe, etc., occur, gloss is lowered, and surface crack occurs.
Accordingly, an object of the present invention is to provide a method for making an ink-jet recording material which has no coating failure or surface crack, and is excellent in gloss and ink absorption property even when a dispersion of silica fine particles having an average primary particle diameter of 50 nm or less are used.
Another object of the present invention is to provide a silica fine particle dispersion and a method for preparing the same, in which aggregation hardly occurs and excellent in dispersibility of the silica fine particles.